1. Field of the Invention
This invention relates to a rubber-cord composite body consisting of a cord for rubber reinforcement such as organic fiber cord, inorganic fiber cord or the like and a rubber composition. More particularly it relates to a technique for improving a bonding property between rubber and cord in the rubber-cord composite body.
2. Related Art Statement
In a rubber-cord composite body consisting of a cord for rubber reinforcement subjected to an adhesion treatment and a vulcanizable rubber composition, there is no problem under ordinary use conditions because the breakage is not caused at a bonding boundary between rubber and cord. Recently, however, the rubber-cord composite bodies have been used under severer use conditions together with the increase of demand in tires for vehicles running under heavy load over a long distance, tires for vehicles running at higher speed, belts and hoses used at higher temperature and the like. Therefore, it is desired to further improve the bonding force between rubber and cord in these cord reinforced rubber articles.
Among the rubber reinforcing cords, it is known that rubber-cord composite bodies obtained, for example, by treating nylon or rayon fiber cords with an adhesive of resorcin.multidot.formaldehyde/rubber latex (hereinafter referred to as an RFL adhesive) have a sufficiently strong bonding force. However, polyethylene terephthalate fiber, polyethylene naphthalate fiber, aramid fiber (for example, Kevlar made by DuPont, Tecnola made by Teijin Limited as a trade name), aromatic polyester fiber, heat resistant fiber having a heterocyclic ring and so on have a rigid skeleton structure, so that they are poor in the affinity with the RFL adhesive. Therefore, the latter fibers are generally treated with an epoxy compound before the treatment with the RFL adhesive or with a resorcin-excessive RFL adhesive having a mol ratio of resorcin or resorcin derivative to formaldehyde of not less than 1.
Furthermore, it has been attempted to treat a non-plated metallic fiber or inorganic fiber such as glass fiber, ceramic fiber or the like with an epoxy compound and further with the RFL adhesive for adhering to rubber.
By the adhesion treatment with the epoxy compound and RFL adhesive, or the adhesion treatment with the resorcin-excessive RFL adhesive was obtained a sufficiently satisfactory bonding force.
However, the rubber-cord composite body is now required to have a very high bonding force, so that the conventional bonding force becomes insufficient under the aforementioned severer conditions. For this reason, it has been attempted to incorporate an adhesion component consisting of methylene acceptor and methylene donor into a rubber composition adjoining the adhesion-treated cord, but there is a drawback that such an adhesion component is resinified in the vulcanized rubber composition to loose the rubbery elasticity and deteriorate the heat build up of rubber.